Corrosion resistant lubricant composition



Patented Sept. 25, 1956 CORROSION RESISTANT LUBRICANT COMPOSITION Ellis K. Fields, Chicago, IlL, assignor to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Application March 30, 1953, Serial No. 345,685

19 Claims. '(Cl. 25232.7)

This invention relates to improved compositions which are effective corrosion inhibitors and which are noncorrosive to silver, silver alloys and similar metals. More particularly, this invention pertains to lubricant compositions which are non-corrosive to such metals and inhibit the corrosion thereof by sulfur and/or corrosive sulfurcontaining compounds.

Advances in the design and construction of internal combustion engines aimed at increased efliciency and economy have led to lubrication problems. To meet the increased severe demands upon engines, many types of lubricant additives have been developed to obtain certain desired characteristics. Among the more effective addition agents which have been developed for compounding with lubricants are many sulfur-containing organic compounds, such as sulfurized terpenes, sulfurized hydrocarbon oils, vegetable oils or animal oils, xanthate esters, organic polysulfide, particularly polyalkyl polysulfides, metal salts of organo-substituted thioacids of phosphorus, metal salts of the reaction product of a phosphorus sultide and a hydrocarbon, such as for example, polybutenes and other poly-olefins, and combinations of the foregoing.

Recent increased use of silver and similar metals in the construction of improved internal combustion engines has created new problems in the use of sulfur-containing additives in lubricants for such engines; the primary problem created being the corrosion of such silver parts of the engine by the sulfur-containing additives. While such corrosion can be eliminated by avoiding the use of sulfurcontaining additives in lubricants for such engines, this solution of the problem is accompanied by the loss of the highly desired beneficial effects of the additives of this type.

It is an object of the present invention to provide a non-corrosive composition. Another object of the invention is to provide a composition non-corrosive to silver and similar metals. A further object of the invention is to provide a composition which will inhibit the corrosion of silver and similar metals by sulfur and/or organic sulfurcontaining compounds. A still further object of the invention is to provide a lubricant composition which is noncorrosive. Still another object of the invention is to provicle a lubricant composition containing an addition agent which will inhibit the corrosion of silver and similar metals by sulfur and/or organic sulfur-containing compounds. A further object of the invention is to provide a method of inhibiting the corrosion of silver and similar metals. Still another object of the invention is to provide a method of lubricating internal combustion engines containing silver and similar metal parts, and inhibiting the corrosion of such metals by lubricants which contain sulfur and/or organic sulfur-containing compounds.

In accordance with the present invention the foregoing objects can be attained by employing in oleaginous materials from about 0.02% to about 10%, and preferably from about 0.25% to about of the oil-soluble reaction product of 2,5-dimercapto-l,3,4-thiadiazole and an unsaturated cyclic compound, particularly unsaturated cyclic hydrocarbons, of at least about five carbon atoms, and preferably from about six to about forty carbon atoms. The proportion of olefin to the dimercapto thiadiazole can vary from 1:1 to 3:1, and reaction temperatures of from about 25 C. to about 150 C., and preferably from about C. to about 130 C. can be employed. The reaction time may vary from about fifteen minutes to forty-eight hours or more, and if desired catalysts such as organic peroxides, azonitriles, ultraviolet light, etc., can be used to accelerate the reaction.

Examples of cyclic olefins suitable for the reaction are styrene, alpha-methyl styrene, pinene, dipentene, vinyl thiophene, vinyl pyridine, cyclohexene, methylcyclohexene, terpinene, terpinolene, sylvestrene, bornylene, cyclopentene, methylcyclopentene, cyclopentadiene, etc.

The preparation of reaction products of this invention is illustrated by the following examples:

EXAMPLE I A mixture of 30 grams 2,5-dimercapto-1,3,4-thiadiazole and 80 cc. commercial dipentene was stirred at l00-120 C. for eight hours. The reaction product Was taken up in 500 cc. hexane and 50 cc. benzene, filtered, and the solvent evaporated off. Eighty grams of an oil-soluble viscous yellow oil having a nitrogen content of 7.47% and a sulfur content of 26.6% was obtained.

EXAMPLE [I A mixture of 45 grams 2,5-dimcrcapto-1,3,4-thiadiazole and 84 grams pinene was stirred at 125 C. for six hours. The reaction product Was dissolved in 500 cc. hexane, filtered, and the solvent evaporated off. Eighty-two grams of an oil-soluble product containing 24.4% sulfur and 7.55% nitrogen was obtained.

EXAMPLE III A mixture of 51 grams of alpha-methyl styrene and 30 grams 2,5-dimercapto-1,3,4-thiadiazole was heated with stirring at -1l5 C. for twelve hours. The reaction product was then cooled to 55 C., filtered and stripped in vacuo, and 74 grams of an oil-soluble viscous clear yellow oil obtained having a sulfur content of 27.3% and a nitrogen content of 8.53%.

EXAMPLE IV A mixture of 21 grams styrene, 15 grams 2,5-dirnercapto-l,3,4-thiadiazole and 50 cc. propanol was refluxed for thirty minutes, and the alcohol and unreacted styrene removed in vacuo. The recovered reaction product was a white solid having a melting point of 103 C., a sulfur content of 36.6% and a nitrogen content of 10.66%.

The structure of the reaction products resulting from the reaction of the dimercapto-thiadiazole and the unsaturated cyclic compounds is not definitely known or capable of being readily determined, since it is difiicult to establish which of the olefinic carbon atoms of the molecule is attached to the mercapto sulfur atom. In the case of alpha-methyl styrene, it is believed the following reaction may take place:

It is believed that short reaction times lead to a predominance of products. of I while products. of. II. or. mixtures of I and II are probably obtained with longer reaction times. The foregoing is merely being postulated and I do'=n'ot wish to be held: thereto;

The above-describedreaction. products can be used in amounts of. from about 0.2% to about 10% and preferably from about 0.25% to about in combination with lubricant base. oils, such hydrocarbon: oils,.synthetic hydrocarbon oils, such as those obtained by the polymerization of hydrocarbons, such as olefin polymers; synthetic lubricating oils of the alkylene-oxide type, for example, the Ucon oils," marketed; by Carbide and Carbon Corporation, the polycarboxylic acid ester type oils, such' as the esters of adipic acid, sebacic acid, maleic acid, azelaic acid, etc.

While the above-described reaction products can be suitably employed alone in combinationwith a base oil, they are usually used in combination with other lubricant addition agents which impart various desired characteristics to the base oil. Usually, these reaction products are used in conjunction with detergent-type additives, particularly those which contain sulfur or phosphorus and sulfur addition agents. This type is usually used in amounts of from about 0.002% to about and preferably from about 0.01% to about 5%. Among the phosphorus and sulfur-containing addition agents are the neutralized reaction products with a phosphorus sulfide and a hydrocarbon, an alcohol, a ketone, an amine or an ester. Of the phosphorus sulfide reaction product additives, l prefer to employ the neutralized reaction products of a phosphorus sulfide, such as a phosphorus pentasullide, and a hydrocarbon of the type described in U. S. 2,316,082, issued to C. M. Loane et al. April 6, 1943. As taught in this patent, stituent of the reaction is a mono-olefin hydrocarbon polymer resulting from the polymerization of low molecular weight mono-olefin hydrocarbons, such as propylene. butenes, amylenes or copolymers thereof. Such polymers may be obtained by the polymerization of mono-olelins of less than six carbon atoms in the presence of a catalyst, such as sulfuric acid, phosphoric acid, boron fluoride, aluminum chloride, or other similar halide catalysts of the Friedel-Crafts type.

The polymers employed are preferably mono-olefin polymers or mixtures of mono-olefin polymers. and isornono-olefin polymers having molecular Weights ranging from about 150 to 50,000 or more, and preferably from about 500 to about 10,000. Such polymers can be obtained, for example, by the polymerization in the liquid phase of a hydrocarbon mixture containing mono.- and isomono-olcfins, such as butylene and isobutylene at a temperature of from about -80 F. to about. 100 F. in the presence of a metal halide catalyst of the Friedel- Crafts type, such as for example, boron fluoride, alumi' num chloride, and the like. In the preparation of these polymers, a hydrocarbon mixture containing isobutylene, butylenes and butanes recovered from petroleum gases, especially those gases produced in the cracking of petroleum oils in the manufacture of gasoline can be used.

Another suitable polymer is that obtained by polymer izing in the liquid phase, a hydrocarbon mixture corn prising substantially C hydrocarbons in the presence of an aluminum chloride-complex catalyst. The catalyst is preferably prepared by heating aluminum chloride with iso-octane. The hydrocarbon mixture is introduced into the bottom of the reactor and passed upward through the catalyst layer, while a temperature of from about 50 F. to about 110 F. is maintained in the reactor. The propane and other saturated gases pass through the catalyst, while the propylene is polymerized under these conditions. The propylene polymer can be fractionated to any desired molecular weight, preferably from about 500 to about 1,000 or higher.

Other suitable polymers are those obtained by polymeras well as other synthetic oils; such as the preferred hydrocarbon conizing a hydrocarbon mixture containing about 10% to about. 25% iso-butylene at a temperature of from about 0 F. to about F., and preferably 0 F. to about 32 F., in the presence of boron fluoride. After the polymerization of the isobutylene together with a relatively minor amount of the normal olefins present the reaction mass is neutralized, washed free of acidic substances, and the unreacted hydrocarbons subsequently separated from the polymers by distillation. The polymer mixture so obtained, depending upon the temperature of reaction, varies in consistency from a light liquid to a viscous oily material and contains polymers having molecular weights ranging from about 100 to about 2,000 or higher. The polymers so-obtained may be used as such or the polymer may be fractionated under reduced pressure into fractions of increasing molecular weight and suitable fractions reacted with the phosphorus sulfide to obtain the desired reaction products. The bot toms resulting from the fractionation of the polymer which have Saybolt Universal viscosities at 210 F., ranging from about 50 seconds to about 10,000 seconds, are well suited for this purpose.

Essentially parathnic hydrocarbons, such as bright stock residuums, lubricating oil distillates, petrolatums, or paraffin waxes, may be used. There can also be employed the condensation products of any of the fore going hydrocarbons, usually through first halogenating the hydrocarbons and reacting with aromatic hydrocarbons in the presence of anhydrous inorganic halides, such as aluminum chloride, zinc chloride, boron fluoride, and the like.

Examples of other high molecular weight olefinic hydrocarbons which can be employed are cetenc (C16), cerotene (C26), melene (can), and mixed high molecular Weight alltenes obtained by cracking petroleum oils.

Other preferred olefins suitable for the preparation of the phosphorus sulfide reaction products are olefins having at least 20 carbon atoms in the molecule of which from about 13 carbon atoms to about 18 carbon atoms, and preferably at least 15 carbon atoms, are in a long chain. Such olefins can be obtained by the dehydrogenation of alkyl halides, preferably long chain alkyl halides, particularly halogenated paraffin Waxes.

As a starting material there can be used the polymer or synthetic lubricating oil obtained by polymerizing unsaturated hydrocarbons resulting from the vapor phase cracking of paralfin waxes in the presence of aluminum chloride. which is fully described in U. S. Patents 1,955,- 260; 1,970,402 and 2,091,398. Still another type of olefin polymer which may be employed in the polymer resulting from the treatment of vapor phase cracked gasoline and/or gasoline fractions with sulfuric acid or solid adsorbents, such as fullers earth, whereby unsaturated polymerized hydrocarbons are removed. The reaction products of the phosphorus sulfide and the polymers resulting from the voltolization of hydrocarbons as described, for example, in U. S. Patents 2,197,768 and 2,191,787 are also suitable.

Other hydrocarbons that can be reacted with a phosphorus sulfide are aromatic hydrocarbons, such as for example, benzene, naphthalene, toluene, xylene, dipheuyl, and the like, or an alltylated aromatic hydrocarbon, such as for example, benzene having an alkyl substituent having at least four carbon atoms, and preferably at least eight carbon atoms, such as a long chain paraffin wax.

The phosphorus sulfidchydrocarbon reaction product can be readily obtained by reacting a phosphorus sulfide. for example, P255 with the hydrocarbon at a temperature of from about 200 F. to about 500 F, and preferably from about 200 F. to about 400 F.. using from about 1% to about 50%. and preferably from about 5% to about 25% of the phosphorus sulfide in the reaction. It is advantageous to maintain a non-oxidizing atmosphere, such as for example, an atmosphere of nitrogen above the reaction mixture. Usually, it is preferable to use an amount of the phosphorus sulfide that will completely react with the hydrocarbon so that no further purification becomes necessary; however, an excess amount of phosphorus sulfide can be used and separated from the product by filtration or by dilution with a hydrocarbon solvent, such as hexane, filtering and subsequently removing the solvent by suitable means, such as by distillation. if desired the reaction product can be further treated with steam at an elevated temperature of from about 100 F. to about 600 F.

The phosphorus sulfide-hydrocarbon reaction product normally shows a titratable acidity which is neutralized by treatment with a basic reagent. The phosphorus sulfidehydrocarbon reaction product, when neutralized with a basic reagent containing a metal constituent, is characterized by the presence or retention of the metal constituent of the basic reagent.

The neutralized phosphorus sulfide-hydrocarbon reaction product can be obtained by treating the acidic reaction product with a suitable basic compound, such as hydroxide, carbonate, oxide or sulfide of an alkaline earth metal or an alkali metal, such as for example, potassium hydroxide, sodium hydroxide, sodium sulfide, calcium oxide, lime, barium hydroxide, barium oxide, etc. Other basic reagents can be used, such as for example, ammonia or an alkyl or aryl-substituted ammonia, such as amines. The neutralization of the phosphorus sulfidehydrocarbon reaction product is carried out preferably in a non-oxidizing atmosphere by contacting the acidic reaction product either as such or dissolved in a suitable solvent, such as naphtha with a solution of the basic reagent. As an alternative method, the reaction product can be treated with solid alkaline compounds, such as KOH, NaOl-l, NazCOs, K2CO3, CaO, BaO, Ba(OH)a, NaeS, and the like, at an elevated temperature of from about 100 F. to about 600 F. Neutralized reaction products containing a heavy metal constituent, such as for example, tin, titanium, aluminum, chromium, cobalt, zinc, iron, and the like, can be obtained by reacting a salt of the desired heavy metal with the phosphorus sulfidehydrocarbc-n reaction product which has been treated with the phosphorus sulfidehydrocarbon reaction product, which has been treated with a basic reagent, such as abovedescribed.

Other phosphorus sulfide reaction products which can be used are the reaction products of a phosphorus sulfide and a fatty acid ester of the type described in U. S. 2,399,243; the phosphorus sulfide-degras reaction products of U. S. 2,413,332; the reaction product of an alkylated phenol with the condensation product of P285 and turpentine of U. S. 2,409,877 and U. S. 2,409,878; the reaction product of a phosphorus sulfide and stearonitrile of U. S. 2,4l6,807, etc.

The silver corrosion inhibiting property of the abovedescribed thiadiazole reaction product is demonstrated by the data in Table I which were obtained by subjecting mixtures of hydrocarbon oil, a neutralized reaction product of P255 and a polybutene, and various herein-described thiadiazolc reaction products to the following test, hereinafter referred to as the modified EMD test:

A silver strip 2 cm. x 5.5 cm. with a small hole at one end for suspension, is lightly abraded with No. 0 steel wool, wiped free of any adhering steel wool, washed with carbon tetrachloride, air-dried and then weighed to 0.1 milligram. Three hundred cc. of the oil to be tested is placed in a 500 cc. liplcss glass beaker and the oil is heated to a temperature of 300 F. (12 F.) and the silver test strip suspended in the oil so that the strip is completcly immersed therein. The oil in the beaker is stirred by means of a glass stirrer operating at 300 R. P. M. At the end of twenty-four hours, the silver strip is removed and while still hot rinsed thoroughly with carbon tetrachloride and air-dried. The silver strip is immersed in a potassium cyanide solution at room temperature until the sil er surface assumes its original bright or silver appearance. The silver strip is then washed successively with distilled water and acetone, air-dried, weighed and loss in weight noted.

The following lubricant compositions were subjected to the above test, and the results obtained are tabulated in Table I.

Table I Silver Sample No. Corrosion (wt. Loss/ Since a weight loss of 20 milligrams is allowable, the ability of 1,3,4-thiadiazole derivatives of this invention to inhibit silver corrosion is demonstrated by the above data.

The effectiveness of the herein-described 1,3,4-thiadiazole derivatives in inhibiting corrosion toward copper and/or lead-containing metals, such as for example, copper-lead alloys, is demonstrated by the data in Table II, obtained by subjecting the above samples to the following test:

A copper-lead test specimen is lightly abraded with steel wool, washed with naphtha, dried and Weighed to the nearest milligram. The cleaned copper-lead test specimen is suspended in a steel beaker, cleaned with a hot trisodium phosphate solution, rinsed with water, acetone and dried, and 250 grams of the oil to be tested together with 0.625 grams lead oxide and 50 grams of a 30-35 mesh sand charged to the beaker. The beaker is then placed in'a bath or heating block and heated to a temperature of 300 F. (:2 F.) while the contents are stirred by means of a stirrer rotating at 750 R. P. M. The contents of the beaker are maintained at this temperature for twenty-four hours, after which the copperlead test specimen is removed, rinsed with naphtha, dried and weighed. The test specimen is then replaced in the beaker and an additional 0.375 gram of lead oxide added to the test oil. At the end of an additional twenty-four hours of test operation the test specimen is again removed, rinsed and dried as before, and weighed. The test specimen is again placed in the beaker together with an additional 0.250 gram of lead oxide and the test continued for another twenty-four hours (seventy-two hours total). At the conclusion of this time, the test specimen is removed from the beaker, rinsed in naphtha, dried and weighed.

The loss in Weight of the test specimen is recorded after each weighing.

This test, known as the Sand Stirring Corrosion Test, is referred to hereinafter as "S. S. C. T.

Table II S. S. O. '1. (mg. Weight Loss) Sample 24 Hrs. 48 Hrs. 72 Hrs.

305 580 i5 185 405 55 415 24 0G l5? :37 Hi 474 Since weight losses of 200 milligrams in 48 hours and 500 milligrams in 72 hours are allowable, the copperlead corrosive inhibiting property of the herein-described 1,3,4-thiadiazole derivatives is clearly demonstrated by the above data.

Under certain conditions it is desirable to use in lubricant compositions elemental sulfur or an organic sulfurcontaining compound of the type hereinabove described either alone or in combination with other additives. Effective lubricant compositions are obtained by the combination of the neutralized reaction products of a phosphorus sulfide and a hydrocarbon, as above described, with elemental sulfur, or ah organic sulfur-containing compound, such as sulfurized mineral oils, sulfurized non-drying animal and vegetable oils, sulfurized olefins and olefin polymers, sulfurized sperm oil, etc., as described and claimed in U. S. Reissue 22,464, issued to C. D. Kelso et al. April 4, 1944, or with sulfurized terpenes, for example, dipentene as described and claimed in U. S. 2,422,585 issued to T. H. Rogers et al. June 17, 1947. While these compounds impart highly desired characteristics to lubricants, and effectively inhibit the corrosion of copper and/or lead, they are corrosive to silver and similar metals. In accordance with the present invention, however, the incorporation in such lubricant compositions of small amounts, namely, from about 0.1% to about 10%, and preferably from about 0.25% to about of the herein-described 1,3,4-thiadiazole derivatives, effectively inhibits the corrosiveness of the silver corrosive compounds without impairing their other desired properties.

Although the invention has been described in connection with the use of the herein-described 1,3,4-thiadiazole derivatives in combination with the one or more secondary additives in lubricant compositions, the invention is not restricted to such use, since these derivatives find utility when used alone in various lubricant compositions or hydrocarbon oil compositions to impart improved and desired characteristics thereto. Thus, for example, these derivatives may be used alone in hydrocarbon oils of high sulfur crudes to inhibit the corrosion of such oils on silver or copper and/or lead-containing metals.

In addition to the aforementioned detergent-type additives and corrosion inhibitors, compositions containing the herein-described derivatives of 2,5dimercapto-l,3,4- thiadiazole can contain other additives, such as antioxidants, pour-point depressors, extreme pressure agents, anti wear agents, V. I. irnprovers, etc.

While this invention has been described in connection with the use of the herein-described additives and lubricant compositions, their use is not limited thereto; but the same can be used in products other than lubricating oils, such as for example, fuel oils, insulating oils, greases, non-drying animal and vegetable oils, waxes, asphalts, and any fuels for internal combustion engines, particularly where sulfur corrosion must be combatted.

Concentrates of a suitable oil base containing more than for example up to 50% or more, of the hereindescribed thiadiazole derivatives alone or in combination with more than 10% of the detergent-type additive and/ or other additives, can be used for blending with hydrocarbon oils or other oils in the proportions desired for the particular conditions of use to give a finished product containing from 0.02% to about 10% of the thiadiazole derivative.

Percentages given herein and in the appended claims :rre weight percentages unless otherwise stated.

Although the present invention has been described with refe ence to specific preferred embodiments thereof, the invention is not to be considered as limited thereto but includes within its scope such modifications and varia tions as come within the spirit of the appended claims.

I claim:

l. A composition comprising a major proportion of an oil containing a compound normally corrosive to silver,

selected from the group consisting of elemental sulfur, a sulfur-containing organic compound and mixtures thereof, and from about 0.02% to about 10% of the oilsoluble reaction product of 2,5-dimercapto-l,3,4-thiadiazole and an unsaturated cyclic hydrocarbon having at least one olefinic double bond and at least about six carbon atoms, said thiadiazole and said unsaturated cyclic hydrocarbon being reacted in the molar ratio of from 3:1 to 1:1 at a temperature of from about 25 C. to about C.

2. A composition as described in claim 1 in which the unsaturated cyclic hydrocarbon is an unsaturated alicyclic hydrocarbon.

3v A composition as described in claim 2 in which the unsaturated alicyclic hydrocarbon is dipentene.

4. A composition as described in claim 2 in which the unsaturated alicyclic hydrocarbon is pinene.

5. A composition as described in claim 1 in which the unsaturated cyclic hydrocarbon is an unsaturated aromatic hydrocarbon.

6. A composition as described in claim 5 in Which the unsaturated aromatic hydrocarbon is a styrene.

7. A composition as described in claim 6 in which the styrene is alpha-methyl styrene.

8. A composition as described in claim 1 in which the oil is a normally liquid hydrocarbon.

9. A lubricant composition comprising a major proportion of a lubricating oil, from about 0.001% to about 10% of a phosphorusand sulfur-containing detergent-type lubricant additive, and from about 0.02% to about 10% of an oil-soluble reaction product of 2,5-dimercapto-l,3,4- thiadiazole and an unsaturated cyclic hydrocarbon having at least one olefinic double bond and having at least about six carbon atoms, said thiadiazole and unsaturated cyclic hydrocarbon being reacted in the molar ratio of from 3:1 to 1:1 at a temperature of from about 25 C. to about 150 C.

10. A lubricant composition as described in claim 9 in which the unsaturated cyclic hydrocarbon is an unsaturated alicyclic hydrocarbon.

ll. A lubricant composition as described in claim 10 in which the unsaturated alicyclic hydrocarbon is dipentene.

12. A lubricant composition as described in claim 10 in which the unsaturated alicyclic hydrocarbon is pinene.

13. A lubricant composition as described in claim 9 in which the unsaturated cyclic hydrocarbon is an unsaturated aromatic hydrocarbon.

14. A lubricant composition as described in claim 13 in which the unsaturated aromatic hydrocarbon is alphamethyl styrene.

15. A lubricant composition as described in claim 9 in which the detergent-type additive is a neutralized reaction product of a phosphorus sulfide and a hydrocarbon.

l6. A lubricant composition as described in claim 9 in which the detergent-type additive is an alkaline earth metal-containing reaction product of a phosphorus sulfide and an olefin polymer.

17. A lubricant composition as described in claim 9 in which the detergent-type additive is a barium-containing neutralized reaction product of a phosphorus sulfide and a hydrocarbon.

18. A composition comprising a major proportion of an oil, from about 0.001% to about 10% of a compound normally corrosive to silver selected from the group consisting of elemental sulfur, a sulfur-containing organic compound and mixtures thereof, and from about 0.02% to about 10% of an oil-soluble reaction product of 2,5- dimercapto-l,3,4-thiudiaz0le and an unsaturated cyclic hydrocarbon. llnving at least one olefiuic double bond and at least about six carbon atoms, said thiadiuzolc and said unsaturated cyclic hydrocarbon being reacted in the molar ratio of from 3:1 to ltl at a temperature of from about 25 C. to about 150 C.

19. A method of inhibiting the corrosion of silver by an oil composition containing active sulfur and normally 9 10 corrosive to silver, comprising incorporating in said oil to 1:1 at a temperature of from about 25 C. to about composition a small amount suflicient to inhibit said cor- 150 C. rosion of an oil-soluble reaction product of 2,5-dimcrcapto-l,3,4-thiadiazole and an unsaturated cyclic hydrocarbon References Cited in the file Of this Patent having at least one olefinic double bond and at least about 5 UNITED STATES NTS 6 carbon atoms, said thiadiazole and unsaturated cyclic hydrocarbon being reacted in the molar ratio of from 3:1 2690999 Lowe et a1 1954 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,764,547 September 25, 195E Ellis K. Fields It is herebjr certified that error a of the above numbered patent requiring c Patent should read as corrected below.

ppears in the-printed specification orrection and that the said Letters Column 8, lines 8, 36, '72, and column 9;, line '7, for "3:1" each occurrence, read l:3

Signed and sealed this 30th day of June 1959.

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Oflicer Commissioner of Patents 

1. A COMPOSITION COMPRISING A MAJOR PROPORTION OF AN OIL CONTAINING A COMPOUND NORMALLY CORROSIVE TO SILVER, SELECTED FROM THE GROUP CONSISTING OF ELEMENTAL SULFUR, A SULFUR- CONTAINING ORGANIC COMPOUND AND MIXTURES THEREOF, AND FROM ABOUT 0.02% TO ABOUT 10% OF THE OILSOLUBLE REACTION PRODUCT OF 2.5-DIMERCAPTO-1,3.4-THIADIAZOLE AND AN UNSATURATED CYCLIC HYDROCARBON HAVING AT LEAST ON OLEFINIC DOUBLE BOND AND AT LEAST ABOUT SIX CARBON ATOMS, SAID THIADIAZOLE AND SAID UNSATURATED CYCLIC HYDROCARBON BEING REACTED IN THE MOLAR RATIO OF FROM 3:1 TO 1:1 AT A TEMPERATURE OF FROM ABOUT 25* C. TO ABOUT 150* C. 